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Report of the Workshop on Analytical Methods for Evaluation of Extinction Risk of Stocks in Poor Condition (WKPOOR1)

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Report of the Workshop on Analytical Methods for Evaluation of Extinction Risk of Stocks in Poor Condition (WKPOOR1) ICES WKPOOR1 REPORT 2009 ICES ADVISORY COMMITTEE ICES CM 2009\ACOM:29 Report of the Workshop on analytical methods for evaluation of extinction risk of stocks in poor condition (WKPOOR1) 18-20 May 2009 Copenhagen, Denmark International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer H. C. Andersens Boulevard 44–46 DK-1553 Copenhagen V Denmark Telephone (+45) 33 38 67 00 Telefax (+45) 33 93 42 15 www.ices.dk [email protected] Recommended format for purposes of citation: ICES. 2009. Report of the Workshop on analytical methods for evaluation of extinc- tion risk of stocks in poor condition (WKPOOR1), 18-20 May 2009, Copenhagen, Denmark. ICES CM 2009\ACOM:29. 21 pp. For permission to reproduce material from this publication, please apply to the Gen- eral Secretary. The document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council. © 2009 International Council for the Exploration of the Sea ICES WKPOOR1 REPORT 2009 | i Contents 1 Opening of the Meeting ............................................................................................... 2 2 Agenda ............................................................................................................................. 2 3 Introduction .................................................................................................................... 2 3.1 Terms of Reference ............................................................................................... 2 3.2 Role of ICES and IUCN ........................................................................................ 3 3.3 Methodology ......................................................................................................... 3 4 Candidate Methods to Evaluate Risk of Extinction ................................................ 5 4.1 Screening Methods ............................................................................................... 5 4.2 Simple Population Viability Analysis Using Time Trends ............................. 5 4.3 Age Structured Population Viability Analysis ................................................. 7 4.3.1 Standard PVA Methods .......................................................................... 7 4.3.2 Adaptation of Standard Fishery Models .............................................. 9 4.4 Comparison of Methods .................................................................................... 10 4.4.1 Screening Methods Compared to Simple PVA .................................. 10 4.4.2 Simple and Age Structured PVAs ....................................................... 11 4.4.3 Detailed Pros and Cons of the three approaches ............................... 11 4.4.4 Summary of methods with respect to TOR: ....................................... 13 5 Discussion ..................................................................................................................... 13 5.1 Methodology ....................................................................................................... 13 5.2 Implications for Management Advice ............................................................. 14 6 Conclusions .................................................................................................................. 15 7 Guidelines for WKPOOR2......................................................................................... 16 8 References ..................................................................................................................... 17 Annex 1 ................................................................................................................................... 18 ICES WKPOOR1 REPORT 20099 | 1 Executive Summary This report summarizes key findings and recommendations of the Workshop on ana- lytical methods for evaluation of extinction risk of stocks in poor condition [ICES WKPOOR1] held in Copenhagen, Denmark, 18-20 May 2009. The report examines a number of general methods to estimate the risk of extinction in exploited marine populations and provides guidance for their application to actual fish stocks. The three general methods examined were: (1) screening methods, (2) simple popula- tion viability analysis based on time trends, and (3) age structured population viabil- ity analysis. These methods were evaluated in terms of information needs, reliability of estimates of extinction risk, and the rates of false positives and negatives. Applica- tion of the guidance provided by this group for specific fish stocks will be made dur- ing a second workshop (ICES WKPOOR2) scheduled for August 2009. A total of five scientists from five countries participated in the workshop. One work- ing document on simulation studies of stock dynamics and routes towards extinction was presented during the WKPOOR1 workshop, and a series of oral presentations dealt with additional simulation studies conducted for the meeting, a general review of population viability analysis, an application of population viability analysis and minimum viable population estimation, and general issues raised in the literature distributed prior to the meeting. This workshop was the result of a request to ICES from Norway for evaluation of the International Union for Conservation of Nature (IUCN) criteria used for redlisting of marine fish species. These criteria are based on screening methods and population viability analysis to classify populations. These criteria have been difficult to apply to exploited marine fish populations in general. This workshop did not create a competing classification system, but rather focused on the provision of pro-active management advice. The workshop ranked screening methods, simple population viability analysis, and age structured population viability analysis low to high for information needs and reliability and high to low for rates of false positives and negatives, respectively. However, none of the methods were considered to produce accurate quantification of the risk of extinction. Screening methods can be misled by expected large changes in exploited marine populations that are not associated with extinction risk. Population viability analysis can be used to compare relative risks of different management op- tions, but absolute risk cannot be estimated due to the final step to extinction usually being caused by a catastrophe, which by definition is a rare event and difficult to predict. The workshop instead suggested examination of the dynamic response of the stock to management as the guiding principle and concluded that fishery models should be used to explore the potential for stocks becoming depleted and potentially going extinct due to a catastrophe. ICES WKPOOR1 REPORT 20099 | 2 1 Opening of the Meeting Chris Legault (USA) welcomed participants to Copenhagen for the meeting of WKPOOR1, a workshop on analytical methods for evaluation of extinction risk of stocks in poor condition. There were five scientists from five countries participating in the meeting (Annex 1). 2 Agenda A formal agenda was not prepared for this workshop. Instead the participants met each day Monday 18 May 2009 through Wednesday 20 May 2009 to discuss topics related to the TOR. Presentations were made on the first day and report writing the focus of the last day. 3 Introduction This workshop was the result of a request to ICES from Norway for evaluation of the International Union for Conservation of Nature (IUCN) criteria used for redlisting of marine fish species. The specific tasks to be considered in the request were: 1. Review of the IUCN criteria and evaluate the suitability and usefulness of using these on marine fish species. Comparison with the ICES system of reference points. 2. Evaluate whether the risk analytical methods currently used by IUCN are suitable for marine fish species, and, if necessary, suggest other and more appropriate methods and procedures. 3. Discuss and suggest procedures and methods within ICES to gather and provide useful biological information about non-commercial species that may improve the redlist evaluation of these species. In response, ICES arranged for two workshops. The first, WKPOOR1, would address methodological issues, while the second, WKPOOR2, would apply the results of the first workshop to a number of species of interest to Norway and ICES. The WKPOOR2 workshop will be held in Bergen, Norway in August 2009 chaired by Dankert Skagen (Norway). 3.1 Terms of Reference The TOR for WKPOOR1 were a ) Review candidate methods for evaluation of risk of extinction for marine fish and shellfish including i ) screening methods, such as those based on relative stock size, the rate of stock decline, etc. ii ) methods that estimate population viability and extinction risk using empirical models that project trends, and iii ) methods that estimate population viability and extinction risk using age structured models and demographic information. ICES WKPOOR1 REPORT 20099 | 3 The methods should be evaluated in terms: - information needs, - reliability of estimates of extinction risk, and - the rates of false positives (when a warning of extinction risk is trig- gered but should not have been), and false negatives (when a warn- ing is not triggered but should have been). This question should also be addressed for situations when it is not possible to evaluate the ex- tinction risks; b ) Identify among the reviewed methods those that are
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